Field of the Invention
The present invention relates to a nanoparticle of an inorganic oxide particle having a reactive group on the surface, a method for producing the nanoparticle, an addition curing silicone resin composition which contains the nanoparticle, and a semiconductor apparatus in which a semiconductor device is encapsulated by the composition.
Description of the Related Art
As an encapsulant for LED, it has been required for a material with high transparency, high refractive index, as well as excellent mechanical properties, heat resistance, and light resistance; and thermoplastic resins such as an epoxy resin, poly(meth)acrylate, and polycarbonate have been frequently used conventionally. Due to a recent trend toward higher output of LED light emitting apparatus, however, it has come to be found that use of these thermoplastic resins causes a problem of heat resistance or discoloration resistance under a condition of a high temperature over a prolonged period of time.
In addition, lead-free solders are often used in recent years when an optical device is soldered to a substrate. The lead-free solders have higher melting point than the conventional solders, and accordingly the soldering have to be generally carried out at a temperature of 260° C. or higher. It has also come to be found that when soldering is carried out such a temperature, encapsulant of the foregoing conventional thermoplastic resin occurs problems such as deformation and yellowing of the encapsulant due to a high temperature.
As described above, encapsulants are required to have more excellent heat resistance compared to previous ones due to a trend toward higher output of LED light emitting apparatus and use of lead-free solders. In order to improve the heat resistance, an optical resin composition in which nano-silica is added to a thermoplastic resin and so on have been proposed (Patent Documents 1 and 2). Thermoplastic resins, however, possess a limitation of heat resistance, and accordingly fail to give sufficient heat resistance.
Silicone resins, which are thermosetting resins, have been studied as an encapsulant for LED since they possessed excellent heat resistance, light resistance, and light transparency (Patent Documents 3 to 5). These silicone resins, however, have lower resin strength and larger gas permeability (i.e., low gas barrier property) compared to epoxy resins, thereby having a disadvantage such as sulfidation of an electrode to cause lowering of the luminance.
In addition, when a silicone resin such as one containing a silicate based fluorescent substance is used as an encapsulant for LED, the silicone resin encapsulant with low gas barrier property is penetrated with water vapor, and the water reacts on the surface of the fluorescent substance to decompose the fluorescent substance. Accordingly, there also arises a problem of considerable lowering of fluorescent property. As described above, when conventional silicone resins are used as an encapsulant for LED, there arises a problem of lowering of a long-time reliability of LED under high humidity as well as a problem of lowering of a luminance due to sulfidation of an electrode. Consequently, a demand for improving gas barrier properties of a silicone resin is now increasing.
As a countermeasure to this, an introduction of an aromatic substituent such as a phenyl group has been studied to increase the refractive index and to improve the gas barrier properties. The introduction of an aromatic substituent, however, increases the change of viscoelasticity at heating, thereby causing a problem of lowering the crack resistance compared to methylsilicone based resins. There also arises a problem of lowering the heat resistance. Accordingly, it has been required to develop an encapsulant with good workability, as well as excellent mechanical properties, transparency, crack resistance, heat resistance, and gas barrier properties after curing.